Removable golf cleats are well known in the prior art. Generally, they include three main features, i.e., a ground-engaging tip, a radial support that firmly rests against the shoe outsole, and an uppermost stem for internal connection (usually by threaded engagement) with a mated socket within the shoe sole. One such receptacle is the subject of U.S. Pat. No. 4,306,360 to Hagger, disclosing an internally threaded receptacle including a plastic body and a metal threaded socket for incorporation into a molded body, e.g., a golf shoe sole. While many early cleats were made solely of metal material, suitably durable synthetics, e.g., hard rubbers or nylons, have been incorporated to varying extents to gain the advantages of lightness of weight, flexibility and attendant comfort in use, and rust-proofness
Extensive use of such synthetics is exemplified in U.S. Pat. No. 2,697,288 to Wilcox, in which the entire cleat structure is uniformly plastic, save for a metal nib inserted at the tip of the ground-engaging head. However, such wholesale replacement of metal with plastic has significant drawbacks; the threaded plastic stem is weak, particularly at the small threadform size that has become standard in the industry, and tends to relax and deform with use, eventuating a looser fit and tendency to unscrew. As most internally threaded receptacles in golf shoes are provided with metal threads, the resultant metal-to-plastic threaded connection (on which there is necessarily much stress, as discussed below) exaggerates this weakness. In the extreme, the plastic threads can be stripped completely from the cleat stem.
U.S. Pat. No. 4,360,490 to Collins also discloses a cleat utilizing a plastic threaded stem, molded uniformly with a plastic support flange; however, the threadform here has been enlarged to a diameter substantially greater than that commonly used in golf cleats, and the plastic stem is made hollow for insertion of a metal pin element which, once inserted, is deformed and riveted over for attachment to the stem. However, while the larger threadform size adds some strength to the plastic stem, this construction eliminates the advantage of using threadforms of the standard, smaller size, while it does not significantly eliminate the tendency of plastic threads to deform when tightly engaged against metal. A further disadvantage lies with the need for ductility in the metal portion of the cleat (i.e., the thin, pin-insert end must be rolled, and then deformed and riveted over for attachment), forfeiting hardness in the ground-engaging head. In such a design, only the tip can then be point-hardened. Thus, the inventor believes that such cleat construction gives up more than it offers.
Other cleats have struck the compromise of retaining an all-metal column (i.e., stem and head portions), in cooperation with an all-plastic support flange. Such a design retains hardness in the head region, a high degree of resiliency in the support, and rust-proof protection by the support of the internal metal connection. However, the inherent challenge of such a design is achieving sufficient affixation of plastic flange to metal column as will tolerate the torque applied in insertion and removal of the cleat (e.g., with the use of special wrenches), the axial forces exerted in use, and the continual flexing of the support member relative to the rigid central column, without causing rupture or separation. Since the primary function of the radial support in a traction cleat is to receive and distribute these forces evenly, efficiently and without threat to cleat integrity, the column-support connection is a crucial one. In the cleat just described, the surface area of attachment, i.e, the metal column-plastic support interface, is localized on the metal column at the latitude of the support, with the result that the loads travelling up the cleat column are concentrated at this narrow junction, prior to their transfer to the support. Thus, the amount of stress at every point of transfer is necessarily greater than it would be were a broader, more stable surface area of attachment provided. The inefficient distribution of forces that results from this construction creates increased vertical rigidity, attendant discomfort to the wearer, potential damage to the integrity of the threaded receptacle, as well as threat of cleat rupture.